Far below is the earth, Above me a bright cloud. I dip and I drop I swoop and I rise-Oh, it's fun to be flying Way up in the skies! There is a painted bus, With twenty painted seats, It carries painted people Along the painted streets. They pull the painted bell, The painted driver stops, And they all get out together At the little. The sun won’t shine forever. Don’t worry, the sun isn’t going anywhere for a very long time. But nothing in the whole universe lasts forever and ever. Our sun will run out of energy in about five billion years. If anyone is around when it happens, they’ll have to leave Earth and find a new planet.
Short version: Earth's average orbital speed is about 30 kilometers per second. In other units, that's about 19 miles per second, or 67,000 miles per hour, or 110,000 kilometers per hour (110 million meters per hour).
In more detail:
Let's calculate that. First of all we know that in general, the distance you travel equals the speed at which you travel multiplied by the time (duration) of travel. If we reverse that, we get that the average speed is equal to the distance traveled over the time taken.
We also know that the time it takes for the Earth to go once around the Sun is one year. So, in order to know the speed, we just have to figure out the distance traveled by the Earth when it goes once around the Sun. To do that we will assume that the orbit of the Earth is circular (which is not exactly right, it is more like an ellipse, but for our purpose a circle is close enough). So the distance traveled in one year is just the circumference of the circle. (Remember, the circumference of a circle is equal to 2×π×radius.)
The Earth Around The Sun Is Called
The average distance from the Earth to the Sun is about 149,600,000 km. (Astronomers call this an astronomical unit, or AU for short.) Therefore, in one year, the Earth travels a distance of 2×π×(149,600,000 km). This means that the speed is about:
speed = 2×π×(149,600,000 km)/(1 year)
and if we convert that to more meaningful units (knowing that there are, on average, about 365.25 days in a year, and 24 hours per day) we get:
speed = 107,000 km/h (or, if you prefer, 67,000 miles per hour)
So the Earth moves at about 110,000 km/h around the Sun (which is about one thousand times faster than the typical speed of a car on a highway!)
Thanks for your explanation, but I was hoping for an explanation a little more precise, since I already knew the one you gave.
In the case of your question about the speed of the Earth around the Sun, there isn't really a more 'precise' answer. The only approximation I did in the calculation I sent you is assuming that the orbit of the Earth is circular. This is in fact a very good approximation. One of Kepler's laws describing planetary motions states that all orbits are ellipses. This is the case for Earth's orbit. But not all ellipses come in the same shape. They are described by their 'eccentricity', which tells us how flattened they are. The eccentricity of an ellipse is a number that varies between 0 and 1, 0 being a perfect circle, and close to 1 being a very flattened ellipse. It turns out that the orbit of the Earth right now has an eccentricity of about 0.017. This means it is almost a circle, making our approximation valid. So under the one approximation that was made, the calculation couldn't really be more 'precise'. And as for the average Earth-Sun distance, the true value changes slightly over time due to gravitational perturbations from the other planets, so there really isn't much point in using a more precise value than the one given above.
Now if you want to calculate the speed of the Earth on its orbit without assuming it is a circle, it is another ball game! First of all, I cannot give you a precise answer, because the speed of the Earth changes all the time as the Earth moves around the Sun. This is because Kepler's second law says that on its orbit, a planet will sweep equal areas in equal amounts of time. This means that when the Earth is closer to the Sun (which happens in early January, about two weeks after the northern winter solstice) it's moving faster than when it is farther away. (For more information on how the Earth's orbital speed varies over the course of a year, please see this answer.) Unless you specified a certain date, this means I cannot give you a precise value for the speed of the Earth assuming its orbit is an ellipse. We are better off to stick with the first number we got - the average speed.
I hope this answers your question now!
This page was last updated on February 28, 2016.
Is the distance from the Earth to the Sun increasing, and if so, by how much in kilometers per (Earth) year?
First I should say that the Earth's orbit around the Sun is elliptical, not perfectly circular, so the Earth-Sun distance is changing as we speak just from the Earth traveling in its orbit around the Sun. See here for a discussion of that.
Earth's Motion Around The Sun
Is the orbit itself changing? Well, there are some long-period oscillations, but those are very small, and don't imply that we're systematically moving towards or away from the Sun.
There is an effect which is making us move very slowly away from the Sun. That is the tidal interaction between the Sun and the Earth. This slows down the rotation of the Sun, and pushes the Earth farther away from the Sun. You can read about tides, as they relate to the Earth-Moon system here. The principle for the Sun-Earth system should be the same. But how big of an effect is this? It turns out that the yearly increase in the distance between the Earth and the Sun from this effect is only about one micrometer (a millionth of a meter, or a ten thousandth of a centimeter). Field training 2ali . So this is a very tiny effect.
There is another effect which is also small, but somewhat bigger than the tidal effect. The Sun is powered by nuclear fusion, which means the Sun is continuously transforming a small part of its mass into energy. As the mass of the Sun goes down, our orbit gets proportionally bigger. However, over the entire main sequence lifetime of the Sun (about 10 billion years), the Sun will only lose about 0.1% of its mass, which means that the Earth should move out by just ~150,000 km (small compared to the total Earth-Sun distance of ~150,000,000 km). If we assume that the Sun's rate of nuclear fusion today is the same as the average rate over those 10 billion years (a bold assumption, but it should give us a rough idea of the answer), then we're moving away from the Sun at the rate of ~1.5 cm (less than an inch) per year. I probably don't even need to mention that this is so small that we don't have to worry about freezing.